Photographic lens.



The drawing; is to scale, but 'thecenters c4 PATENT OFFICE.

HUGH LANCELOT ALDIS, OF COUNTY OF MIDDLESEX, ENGLAND.

PHOTOGRAPHIC LENS.

SPECIFICATION form-ing part of Letters Patent No. 682,017, datedSeptember 8, 1901. Application led February 4, 1901. Serial No. 45,900.CNO model.)

To all whom it may concern.-

Be it known that l, HUGH LANcELo'r ALDIs, optician, a subject of theQueen of Great Britain, residing at 65 Lauderdale Mansions,

Lauderdale road, in the county of Middlesex,

England, have invented certain new and useful Improvements Relating toPhotographic Lenses, of which the following is a specification.

lo The object of this invention is with the greatest simplicity tocorrect the five spherical aberrations known as, first, ordinaryspherical aberration; second, coma; third, curvature of field; fourth,astigmatism; fifth,

r 5 distortion, and also the two chromatic aberrations; sixth,longitudinal chromatic aberration; seventh, chromatic error ofmagnification. For this purpose I employ a doublet composed of twocomponents-viz., one como ponent a cemented combination of long focuseither slightly positive or slightly negative) formed of aconverging-lens cemented to a diverging-lens of slightly-higherrefractive index; the second component a converging-lens of highrefractive index.

The drawing shows a lens constructed according to this invention.Preferably the top is the front; but it also works well the other way.

3 0 The compound lens is made up of three glasses A, B, and C, Aand Bbeing cemented together.

c' is the center of the outer face of A, and R is its radius. l

o2 is the center of the cemented faces of A and B, and R2 is theirradius.

c3 is the center of the inner face of B, and RS is its radius.

c4 is the center of the inner face of C, and R4 4o is its radius.

c5 is the center of the outer face of C, and R5 is its radius. l

t', t2, and t4 are the thicknesses of A, B, and C, respectively, and t3is the distance betwel the centersvof the inner surfacesof B and c5 areshown much nearer tothe lens than they really are The refractive indicesof the glasses em- 5o ployed for the lenses A, B, and O are- D Zine. H yZine.

A 1.5366 1.5508 B 1.5738 1.5920 c... 1.6014 1.6199

For the purpose of attaining the object of this invention it isessential that in addition 7o to the employment of glasses of varyingindices of refraction as hereinbefore described, there shall be fiverefractive surfaces (of which three are positive or light-converging andtwo negative or light diverging) and 75 that the apparent centers ofsuch surfaces, taken in the order in which they occur along the opticalaxis of the system, shall correspond with a positive and a negativesurface alternately. Thus, counting from the top to 8o the bottom of thedrawing, c5 is the apparent center of the positive or converging surfaceR5. c2 is the apparent center of the negative or diverging surface R2. cis the apparent center of the positive or converging surface R. c3 isthe apparent center of the negative or diverging surface R3. c4 is theapparent center of the positive or converging surface R4.

By the term apparent center in the foregoing description I meantheposition at which 9o the true center of a refracting-surface willappear to the eye 0f au observer lookingy through the system.

By theemployment of not less than fiverefracting-surfaces having theaforesaid order or disposition of the apparent centers on the opticalaxis the aberrations hereinbefore referred to are simultaneouslycorrected, so that the image produced by the combined system of lensesis free from the same.

What I claim isl. The combination of a component con` sisting of aconverging-lens and a diverginglens cemented together, and a secondcomponent consisting of one double convex lens the radius of curvatureof each of the two faces of the second component being greater than theradius of curvature of any face of the first component, and the radiusof curvature of the outer face of the second component being greaterthan that of its inner face.

2. The combination of a component consisting of a converging-lens and adiverginglens cemented together, and a second component consisting ofone double convex lens the radius of curvature of each of the two facesof the second component being greater than the radius of curvature ofany face of the first component, the radius of curvature of the outerface of the second component being greater than that of its inner face,and the ap- `parent centers of curvature of the faces being in theorder: center of outer face of second component, center of cementedfaces of first component, center of outer face of first component,center of inner face of first component, and center of inner face ofsecond component. y

3. The combination of a component consisting of a converging-lens and adiverginglens cemented together, anda second component consisting of onedouble convex lens the radius of curvature of each of the two faces ofthe second component being greater than the radius of curvature of anyface of the first component, the radius of curvature of the outer faceof the second component being greater than that of its inner face, theradius of curvature of the cemented faces of the first component beinggreater than that of either of its other two faces, and the radius ofcurvature of its outer face being greater than that of its inner face.

4. The combination of a component consisting of a converging-lens and adiverginglens cemented together, and a second component consisting ofone double convex lens the radius-of curvature of each of the two facesof the second component being greater than the radius of curvature ofany face of the rst component, the radins of curvature of the outer faceof the second component being greater than that of its inner face, theradius of curvature of the cemented faces of the rst component beinggreater than that of either of its other two faces, theradius ofcurvatureof its outer face being greaterthan that of its inner face, andthe apparent centers of curvature of the faces being in the order:center DEiAFTeMAN.

of outer face of second component, center of cemented faces of firstcomponent, center of outer face of rst component, center of inner faceof first component, and center of inner face of second component.

5. The combination of a component consisting of a converging-lens and adiverginglens cemented together, and a second component consisting ofone double convex lens the radius of curvature of each of the two facesof the second component being greater than the radius of curvature ofany face of the first component, the radius of curvature of the outerface of the second component being greater than that of its inner face,the refractive index of the diverging-lens of the first component beinghigher than that of its cons verging-lens.

6. The combination of a component con'- sisting of a converging-lens anda diver-ging lens cemented together, and a second component consistingof one doubleconvex lens the radius of curvature of each of the twofaces of the second component being greater than the radius of curvatureof any face of the first component, the radius of curvature of the outerface of the second component being greater than that of its inner face,and the apparent centers of curvature of the'faces being in the order:center of outer face of seco-nd component, center of cemented faces offirst component, center .of outer vface of rst component, center ofinner face of first component, center of inner face of second component,the refractive index of the di verging-lens of the first componen-tbeing higher than that of Vits converging-lens.

7. The combination of a component con sisting of a converging-lens and adiverging= lens cemented together, and a second compo nent consisting ofone double convex lens the radius of curvature of each of the two facesof the second component being greater than the radius of curvature ofany face of the rst component, the radius of curvature of the outer faceof the second component being greater than that of its inner face, theradius of curvature of the cemented faces of the first component beinggreater than that of either of its other two faces, the radius ofcurvature of its outer face being greater than that of its inner face,the refractive index of the diverging-lens of the first component beinghigher than that of its converging-lens;

8. The. combination of a component con sisting of a converging-lens anda diverginglens cemented together, and a second component consisting ofone double convex lens the radius of curvature of each of the two facesof the second component being greater than the radius of curvature ofany face of the first component, the radius of curvature of theouterface of the second component being greater than that of its innerface, the radius of curvature of the cemented faces of the IIO lav verrst component being greater than that of center of inner face of secondcomponent, the mfg: either of its tiierT-'two faces, the radius ofrefractive index ofthe diverging-Iens of the curvature of its outer facebeing greater than rst component4 -being higher than that of its that ofits inner face, and the apparent cenconverging-lens;V ters of curvatureof the faces being in the or-y der: center of outer face of secondcompo- HUGH LANCELOF ALDIS nent, center of cemented faces of first com-Witnesses: ponent, center of outer face of first compo- FREDK. C;WEATHERLY, nent, center of -inner face of first component, H. A.MARSHALL.

